If Amazon launched on-line services it would not be good for other companies in this business. I have heard time and time again that Amazon members have asked Amazon to do so. From knowing the business plan desires of Zoties they will cut deep into the business of prescription services. I like a couple of on-line pet companies, but yes they could take a fatal hit from several directions.
I would say Amazon COULD be a threat but we have to wait and see. The online services of precription from big box retailers such as Walmart and Target have been in business for a while but it turns out it is not a big problem for PETS. I am not worrying about Zoties at all for now.